The Cospas-Sarsat System provides distress alert and location information to search and rescue (SAR) services throughout the world for maritime, aviation and land users in distress. The System is comprised of:

satellites in Low-altitude Earth Orbit (LEOSAR) and Geostationary Orbit (GEOSAR) that process and / or relay signals transmitted by distress beacons; ground receiving stations called Local User Terminals (LUTs) which process the satellite signals to locate the beacon; and Mission Control Centres (MCCs) that provide the distress alert information to SAR authorities.

The Cospas-Sarsat System can detect and locate distress beacons that operate at 406 MHz. Satellite processing of old analogue technology beacons that transmit at 121.5 MHz ended on 1 February 2009.

To understand the options available, we first have to understand the satellite constellations and emergency support networks that support each device. Currently, there are three major systems:

1. COSPAS/SARSAT, non-profit network which supports PLBs This satellite constellation is the largest and most complete, and is essentially military. It has provided the satellite support used for Emergency Position Indicating Radio Beacons (EPIRBs), which are designed exclusively for marine use, for more than 30 years. Over 33,000 people worldwide have been rescued as a result of this network since the program’s inception. COSPAS/SARSAT now also supports PLBs, which are essentially EPIRBs for land-lubbers. It is very important to understand that a PLB is not a SPOT! This network covers the entire planet.

2. Globalstar, a for-profit communications network that supports the SPOT devices in this review: The Globalstar corporation launched 52 satellites by 2000 to support a satellite phone communication network. It currently does not cover polar regions or sub-Saharan Africa (map: http://www.globalstar.com/en/index.php? ... sidenav=85); A series of problems with satellites from its first constellation launch was supposedly addressed in 2011 and 2012 with the launch of several additional satellites, but the total efficacy of their current network is still widely questioned.

3. Iridium, a for-profit communications network that supports the DeLorme InReach:The Iridium network contains approximately 77 satellites that cover the entire planet, including polar regions. Its track record over the past 5-6 years has been less blemished than that of Globalstar’s, but whether it still outperforms Globalstar is a matter of debate (For the record, the Iridium-supported device we tested worked more often than the Globalstar-supported devices).

Now that we have a basic understanding of the satellites, let’s talk devices: PLBs A PLB does not require a paid annual subscription to send an SOS message. It transmits an SOS message with GPS coordinates via satellite, and in addition to that, emits a homing signal on the 121.5 MHz emergency frequency, at a power level 5 to 10 times higher than a SEND (SPOT or InReach) device. Furthermore, the PLB is much more likely than a SEND device to acquire the satellites necessary for a GPS coordinate lock.

A PLB emitting a distress signal in these two manners absolutely represents your best chance of being located and at this most basic level is a better device than anything operating on Globalstar or Iridium. That is to say, when it comes down to the nitty-gritty and you press that SOS button, a transmitting PLB is far more likely to get you rescued than a SEND device. Don’t forget this.

SEND (Satellite Emergency Notification Devices) (SPOT & DeLorme)These devices require a paid annual or monthly subscription and transmit on a higher frequency (1610 MHz) to a commercial Rescue Coordination Center operated by Globalstar or Iridium. If you don’t pay, you don’t get rescued (It’s interesting to note that even when you don’t pay your mobile phone bill, you can still dial 911).

If all I cared about was getting rescued when I pressed the SOS button, I would not have written this review because choosing a PLB instead of a SPOT would be a no-brainer, and I would be encouraging all of my friends to ditch their SPOTs and get a real PLB device. But it’s more complex than that, and the additional features available with the SPOT and DeLorme devices reviewed here make them worth considering.

SEND devices transmit your GPS coordinate location only, and not all of the time. The SPOT 2 transmits its signal at one-tenth of the strength of the ResQLink, and there have been many documented cases of the SPOT 2 not transmitting an SOS successfully, and / or transmitting an SOS message without a GPS lock, which tells authorities and your contacts that you’re in trouble, but not where you are. SEND devices do not emit the additional homing signal on 121.5 MHz. Also, the 5 watt 406 MHz PLB signal emitted by a PLB can be used by rescuers to establish an approximate location, whereas the SEND device’s less powerful signal cannot be used in that way. If your SEND device can’t get your GPS coordinates out due to line-of-sight obstructions, you’ll wish that you’d bought a PLB instead.

Power and Frequency Differences:Power and Frequency are two key areas to consider when researching a life saving device. Satellites are thousands of miles away from earth, so your beacon’s signal needs to have enough power to travel that far and be able to go through anything between you and the satellite (trees, weather, out of slot canyons, etc.).

POWER: SPOT is powered by 400 milliWatts while ACR 406 MHz PLBs and EPIRBs use 5 Watts. You would need 12.5 SPOT units to equal the POWER of one ACR PLB or EPIRB! When your signal has to travel 22,000 miles to reach a satellite, you want to make sure you have more than enough power to get it there!

FREQUENCY: The basic principles of frequency are that the lower the frequency, the easier it can penetrate buildings, trees and meteorological activity that appear between the transmitting device (PLB, EPIRB or SPOT) and the receiving device (the satellites). FM radios and TV channels work on a lower frequency which is why they can penetrate buildings and the environment pretty easily. Now think about radar which uses a really high frequency. Radar works by hitting an object and bouncing off, that’s how radar knows where to place an airplane on the radar screen. So the higher the frequency, the less likely it can penetrate things in between, the lower the frequency, the easier it can penetrate. 406 MHz PLBs and EPIRBs use a dedicated frequency set up by the search and rescue community that is in the same range as UHF TV stations. SPOT uses the 1.6GHz frequency which is four times higher in the frequency spectrum. This means SPOT’s frequency is four times less likely to go through an object or weather than the lower 406 MHz frequency.

Considering power, combined with frequency, ACR’s 406 MHz beacon stands head and shoulders above satellite messenger systems like SPOT. ACR has 12.5 times more power and is four times more likely to penetrate objects in between the beacon and the satellite than SPOT.

Redundancies: PLBs and EPIRBs have multiple ways to contact SAR in order to get you rescued. SPOT has one single transmission method. PLBs and EPIRBs can contact SAR via 406 MHz, which locates your beacon using Doppler Shift, it can contact SAR using GPS data and it also has a 121.5 MHz homing frequency so when SAR forces get a few miles away from you, they can home in directly on your beacon and find you faster. SPOT uses GPS only to send its location. If you cannot download GPS, SAR will have no idea where you are!

Coverage: EPIRBs and PLBs use the Cospas-Sarsat satellite system which contains 2 different satellite systems (LEOSAR – Low earth orbiting and GEOSAR – Geostationary). These two systems cover every inch of the planet. SPOT tracker is part of Globalstar and uses the Globalstar (Nasdaq: GSAT) satellite system which only covers a certain percentage of the earth, but has quite a few locations that are undetectable.

The SPOT is an excellent tool for personal tracking and checking in with friends and family to say “I’m OK”. In fact, I own a SPOT myself and carried one on a remote 6 week kayaking expedition in the Pacific North West last summer – I was able to check in every few days and send my friends GPS coordinates so they can track the progress of the expedition. However, the SPOT was brought purely for those tasks, not for emergency use – for emergency use I wanted to ensure that I had a device that was certified to the highest standards, was fast, and provided more than just GPS signaling – for these reasons I carried an ACR SARLink GPS equipped PLB.

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